Was going to post this for the last chapter, but here works too. My biggest issue with the shady assembly, is that some of the goals of their membership have a chasm too large to bridge. I mean, you have a faction that wants to get rid of the nobility and a faction that hates the commoners and wants to make them less relevant. I'm sorry, you don't those two factions to ally even if you have other factions as intermediaries. They are too diametrically opposed in their goals and no way in hell they look past those goals for some common goal.
Not to mention that the goals of said group are too diverse and conflicting for them to really keep their presence from being known. You'd get enough infighting and different interests, that their existence would have been leaked.